Method and apparatus for electrostatic flocking



A. CHMELAR Dec. 29 1970 METHOD AND APPARATUS FOR ELECTROSTATIC FLOCKING'2 Sheets-Sheet 1 Filed April 14, 1967 0 4 W 5 m Tl AO/S CHMELAE ATTORNE'YS" Dec. 29, 1970 A. CHMELAR 8 METHOD AND APPARATUS FOR ELECTROSTATICFLOCKING Filed April 14 1967 2 Sheets-Sheet z 'INVENTOR4 ALO/ CH/VIELARATTORNEYS United States Patent Oflice 3,551,178 Patented Dec. 29, 19703,551,178 METHOD AND APPARATUS FOR ELECTROSTATIC FLOCKING Alois Chmelar,Dearborn, Mich., assignor to Velvetex Industrial Corporation, Detroit,Mich., a corporation of Michigan Filed Apr. 14, 1967, Ser. No. 631,074Int. Cl. B44c 1/08; Bb 5/02 US. Cl. 117-'-17 11 Claims ABSTRACT OF THEDISCLOSURE Method and apparatus for electrostatic application of flockcoating are disclosed. An electrostatic flocking machine includes aportable hand-held applicator having an electrode therein which isenergized to establish an electrostatic field between the electrode anda wall that is to be flocked with fibers. There is a bulk fiber storagereceptacle separate and remote from the applicator. Loose fibers areblown from the receptacle through a duct to the applicator. The airwhich transports the fibers from the receptacle to the applicator ispreferably humidified to enhance the electrostatic deposition of thefibers onto the wall. The applicator includes a baffle and screenarrangement which separates the moving fibers from the moving air anddirects the fibers downwardly in front of the electrode and into thefield. The baifles are constructed so that the fibers fall downwardlytoward the electrode primarily due to gravity. The screens allow movingair to esca e from the applicator and substantially eliminate or, at theleast, greatly reduce the effect of the moving air on the motion of thefibers just before the fibers are introduced into the electrostaticfield.

This invention relates to electrostatic application of fiber-coatingsand more particularly to a method and apparatus for continuously feedingloose fibers into an electrostatic field during an electrostaticflocking operation. The present invention is particularly useful withelectrostatic methods and apparatus wherein a hand-held applicator isused to apply fiber-coatings to a wall and the like such as disclosed inmy copending application entitled Electrostatic Flocking, Ser. No.382,501, filed July 14, 1964 now abandoned and in US. Pat. No.2,706,963, entitled Device for Fiber-Coating Materials and Objects andgranted to Rudolf Hug on Apr. 26, 1955. In one embodiment of theinvention of my aforementioned application and also in theaforementioned Hug patent (FIG. 4), a portable hand-held applicator isused in fiber-coating or flocking a wall. The applicator carries oneelectrode and also serves as a fiber container. Fibers are disposed inthe container so that they can be introduced, as by shaking theapplicator, into an electrostatic field created by the electrode.However, the applicator has only limited fiber storage capacitycompatible with manual manipulation of the applicator and thus whenflocking walls or other large areas, the flocking process must beinterrupted from time to time to refill the applicator with fibers. Thisdecreases the efliciency of the flocking operation and thus increasesthe cost thereof. Small size and lightweight construction of theapplicator are limited to some extent by the electrode configuration.Thus, if an applicator is constructed to have greater fiber capacity itwill be larger, heavier and bulkier, making the applicator difficult tomanipulate and the work load greater.

The present invention contemplates a method and an apparatus ofelectrostatic flocking, particularly of the type referred to hereinabovewherein the flocking fibers are stored in a receptacle separate andremote from the portable applicator. During a flocking operation, thefibers are blown from the receptacle through a flexible hose to theapplicator to continuously supply fibers as required by the flockingoperation. By this arrangement, the size and weight of the applicatorcan be reduced and effective flocking is achieved more efiiciently, withless work and greater ease in handling of the applicator by comparisonto the aforementioned prior art techniques. Humidity control and aparticular construction of the applicator are also contemplated by thepresent invention to further improve the flocking operation.

Thus, the objects of the present invention include providing methods andapparatus of electrostatic flocking that overcome the aforementioneddisadvantages; that provide uniform and controllable introduction offibers into the electrostatic field; that provide a simple arrangementfor moistening fibers when required and thus further improve theelectrostatic flocking operation; that are easier to employ, requireless work and are more efiicient and more economical by comparison toprior art techniques.

Other objects, features and advantages of the present invention willbecome apparent in connection with the following description, theappended claims and the accompanying drawings in which:

FIG. 1 diagrammatically illustrates an operator using a portableapplicator to apply flocking material to a wall according to the presentinvention;

FIG. 2 is a view, partly broken away and in section, of apparatus forstoring bulk fibers and blowing the fibers to the hand-held applicator;

FIG. 3 is a fragmentary horizontal section taken on line 33 of FIG. 2 toillustrate a sifter outlet construction of a fiber storage bin;

FIG. 4 is a horizontal section taken on lines 44 of FIG. 3;

FIG. 5 is a perspective view of the portable applicator;

FIG. 6 is a front view, partly broken away and in section, of theapplicator;

FIG. 7 is a vertical section taken on line 77 of FIG. 6; and

FIG. 8 is a horizontal section taken on line 88 of FIG. 7.

FIG. 1 illustrates an operator 10 applying flocking fibers to theexposed surface 14 of a solid wall 16 with a handheld applicator 18.Surface 14 is coated with a layer of conductive adhesive 20 which in thepreferred embodiment is treated by adding finely divided metallicparticles thereto to increase the conductivity of the adhesive. Aportable direct-current power supply has one of its output terminals(not shown) connected via a shielded lead 24 to an electrode 28 inapplicator 18. In the illustrated and preferred embodiment of thepresent invention, the other output ter minal of the power supply 22need not be connected to either wall 16 or adhesive 20 for performingthe flocking operation as set forth in greater detail in myaforementioned prior application. However, the present invention alsocontemplates a two-lead system such as disclosed in the aforementionedHug patent wherein the other output terminal from power supply 22 iselectrically connected to the adhesive coated wall 16 so that wall 16serves as a second activated electrode. Reference may be had to eithermy prior application or to the aforementioned Hug patent for furtherdetails of the system thus far described and the operation thereof bywhich fibers can be electrostati cally deposited on wall 16.

In accordance with one important aspect of the present invention, thereis a fiber storage and blowing unit 30 which is connected to applicator18 by a flexible hose 32 to continuously supply fibers to the applicator18 during a flocking operation. Referring to FIGS. 2-4, the unit 30generally comprises a housing 31 divided generally into an upper section33, a middle section 34 and a bottom section 36. Mounted in the topsection 33 of housing 31 is a cylindrical receptacle or bin 38containing bulk flock ing fibers generally indicated at 40. The bottomof bin 38 is formed with a radially inwardly projecting, annular flange42. A circular bottom plate 44 is mounted in the lower portion of bin 38spaced just above flange 42. Plate 44 has a pair of openings 46 whichserve as an outlet for the bin. The effective size of the outletopenings 46 is controlled by an adjustable gate plate 48 rotatablymounted in the space between plate 44 and flange 42. Plate 48 has ahandle 49 which extends radially outwardly therefrom through suitableopenings in the bin 38 and housing 31 so that an operator can adjust thefiber flow rate through outlet openings 46. A motor 50 is suitablymounted on housing 31 below and centrally of bin 38. Motor 50 drives asifter blade 52 disposed above plate 44 to agitate fibers 40 and thusfacilitate flow thereof through the outlet openings 46. A screen 54 ismounted on top of plate 44 below blade 52 to block passage ofagglomerated fibers. The upper section 33 also has a removable cover 56for access thereto as when filling bin 38. The upper section 33 ispreferably hinged to the middle section 34 to provide easy access to themiddle section 34.

The upper section 33 is separated from the middle section 34 by agenerally horizontal partition 58 removably mounted on housing 31 andhaving an opening therein aligned with the outlet of bin 38. A Conicalhopper 60 is mounted in the middle section 34 of housing 31 as by rigidsuspension on partition 58. Hopper 60 is disposed directly below bin 38to receive fibers 40 passing through the outlet openings 46. The top ofhopper 60 is spaced below partition 58 to provide a vent through whichair is drawn into the hopper. At one side of housing 31 is an outsidevent 62 communicating with the middle section 34. The effective size ofvent 62 can be varied by an adjustable gate 64. Preferably, housing 31is reasonably airtight except for vent 62 so that all the air flowthrough the unit 30 can be effectively controlled. However, specialprecautions are not necessary since generally the air flow does notrequire narrow tolerance control.

The middle section 34 is separated from the lower section 36 by apartition 66 removably mounted on the lower section. Hopper 60 has atubular outlet portion 67 which passes downwardly through a suitableopening 68 in partition 66. A flat rigid gasket 69 is mounted on thehopper portion 67 to seal the opening 68. The hopper outlet portioncommunicates with the inlet of a centrifugal blower 70 mounted in thelower section. Blower 70 is driven by a motor 72 and has an outlet 73which passes outwardly through housing 31 and is connected to hose 32.The lower section 36 also houses a humidifier indicated generally at 74for adding moisture to the air being drawn through the middle section34. Various types of humidifiers may be used but for purposes ofillustration, humidifier 74 is shown as comprising a water tank 75formed by a transverse wall 76 in the lower section 36. An atomizer 78is mounted in tank 75 with its outlet communicating upwardly throughpartition 66 and into housing section 34 so that atomized waterparticles are directed into the air drawn through port 62.

Also in the preferred embodiment, the middle section 34 is hinged orotherwise removably secured to the lower section 36 to provide access toblower 70 and humidifier 74. It is also desirable but not essential thatpartitions 58, 66 are constructed so that excessive moisture andcondensation in the middle section 34 cannot readily pass into eitherthe upper section 33 or the lower section 36. Suitable electricalconnections are made to sifter motor 50, blower motor 72 and atomizer'78. The speed of blower 70 can be varied by means of suitableelectrical controls 79 for motor 72. The atomization rate of theatomizer 78 may also be made variable by suitable controls, although anOn-Ofi atomizer can provide satisfactory humidity control for mostapplications.

Referring more particularly to FIG. 8, the applicator 18 is formed witha rear inlet section 86 and a front outlet section 88. In general, theinlet section 86 receives the air and entrained fibers 40 from hose 32,separates the moving fibers 40' from the moving air and delivers thefibers to the front section 88 where they are directed downwardly intothe electrostatic field primarily under the influence of gravity. Moreparticularly, the applicator end of hose 32 is fastened on a supportingsleeve 90 which passes through and is fastened on a rear wall 94 toserve as a handle and an inlet for applicator 18. The rear section 86has side walls 96 which converge forwardly and laterally inwardly fromthe rear wall 94 to a back wall 98 of the front section 88. The sidewalls 96 extend the full height of the applicator. An inclined partition100, trapezoidal in shape, is fastened at its lower rear end to wall 94below the sleeve 90. Partition 100 extends transversely between the sidewalls 96 and is inclined forwardly and upwardly with its forward edgejoined to wall 98 just below the top of the applicator at the bottom ofa rectangular cutout 112 in the wall 98.

Partition 100 has a rectangular opening 102 therethrough disposeddirectly in front of sleeve 90 and covered by a fine mesh silk screen104. A flat stop or plate 105 is slidably mounted on the underneath sideof partition 100 to adjust the effective size of the opening 102. Airentering the rear section 86 can :pass freely through screen 104 whereasthe fibers 40 cannot and thus partition 100 and screen 104 deflect thefibers upwardly and forwardly in section 86 while permitting some of themoving air to pass through the screen and out of the lower open end ofsection 86. The entire top of the applicator 18 is also open and iscovered by a second fine mesh silk screen 106 to permit moving air topass freely therethrough while containing fibers 40 Within theapplicator.

The cutout 112 at the top of wall 98 extends transversely between theside walls 96. Fibers directed upwardly by partition 100 pass from therear section 86 through cutout 112 into the front section 88. Directlyin front of cutout 112 is a bafile 114 which extends the full width ofthe front section and is inclined downwardly and rearwardly from the topscreen 106 toward wall 98 with the lower edge of the baffle generallyhorizontally in line with the bottom of cutout 112. Baflle 114 catchesthe fibers 40 entering the front section 88 through the cutout 112 andcauses the fibers to fall downwardly from the baflle. Any air movingthrough the cutout 112 is directed upwardly by baffle 114 through thetop screen 106. The lower edge of bafi le 114 is spaced forwardly ofwall 98 to form a slot-like aperture 116 across the full width ofsection 88 through which fibers can fall toward electrode 28.

Electrode 28 is contoured sheet metal which extends substantially thefull width of the front section 88. The top edge of electrode 28 isfastened to wall 98 slightly below the bottom of cutout 112. A flat topportion 120 of electrode 28 inclines forwardly and downwardly to aforwardly projecting ridge portion 122. The top surface of the ridge 122is generally horizontal. The electrostatic field will be strongest inthe vicinity of the ridge portion 122 since it is closest to the wall 16being coated. Some of the fibers falling through aperture 116 will enterthe field in front of the inclined electrode portion 120 and bepropelled to the wall 16. However, most of the fibers, or at least asubstantial portion thereof, will strike the inclined electrode portion120 and fall downwardly onto the top of ridge portion 122 where they aresubjected to the strongest field and rapidly propelled to vvall 16. Thefiat horizontal top of ridge portion 122 assists in aligning the fibershorizontally as they are propelled by the field to wall 16. The contourof electrode 28 returns from the ridge portion 122 downwardly andslightly rearwardly to the bottom of the front section 88.

The front of the applicator 18 is closed by a removable screen spacedforwardly of electrode 28. Screen 140 is slideable in a guide formed inthe side walls of section 88. The mesh size of screen 140 issubstantially greater than the mesh of the screens 104, 106 so thatindividual fibers can pass freely through the mesh of the screen 140.The mesh size of screen 140 can be substantially less than the length ofthe individual fibers since it has been found that the fibers tend toalign with the field in a direction between electrode 28 and the objector wall 16. However, the mesh size is chosen small enough to preventfibers from falling out of the applicator 18 unless they are alignedgenerally perpendicular to the screen.

The shielded lead 24 is connected to the lower portion of the electrodeplate 28 and extends rearwardly therefrom through a second supportingsleeve 130 mounted on wall 94. Sleeve 90 is intended to serve as themain handle for applicator 18 whereas sleeve 130 serves as an auxiliaryhandle when the operator desides to use both hands. With the exceptionof electrode 28 and the electrical connections to lead 24, all of theremaining parts of the applicator 18 described hereinabove are formed ofsuitable insulating material.

To summarize the electrostatic flocking described hereinabove, theoperator turns on power supply 22, sifter motor 50, blower 70 andatomizer 78. The sifter blade 52 agitates fibers 40 in bin 38 and causesthem to fall downwardly through the outlet Openings 46 and into thehopper in a free-falling loose condition. Blower draws air into themiddle section 34 through vent 62 and over the top of the hopper whereit picks up the fibers. The air entering vent 62 also picks up moisturein passing through section 34 and above atomizer 78. Loose fibersentrained in the air are drawn into blower 70 and then blown throughhose 32 to applicator 18. By adjusting the speed of motor 72 andadjusting the stops 48, 64, the quantity of fibers 40 supplied toapplicator 18 and the quantity of air necessary to transport the fiberscan be selected as required.

As the fibers entrained in the air enter the applicator 18 throughsleeve 90, they are deflected upwardly and forwardly by partition andscreen 104 toward cutout 112.,Some of the air will pass through screen104 and out of the lower open end of the applicator. The effective sizeof opening 102 is set by step 105 so that the air remaining issufiicient to carry all of the fibers upwardly to cutout 112. As thefibers pass through cutout 112, they will either drop directly throughaperture 116 or they will impinge upon bafile 114 and then fall downwardthrough the aperture 116. Substantially all of the moving air remainingwill pass upwardly through screen 106 at the top of the applicator.Thus, the motion of the fibers as they pass through aperture 116 is duealmost entirely to gravity and to some extentto the electrostatic field.Stated differently, the motion of these fibers as they drop downwardlyonto electrode 28 is substantially free from the effect of the movingair which brought them to the applicator. This relatively inertmotion ofthe fibers as they drop downwardly into the electrostatic field permitsthe electrostatic field to effectively align the fibers and propel themto the object being coated. As a practical matter, some excess airpassing through cutout 112 may pass downwardly through aperture 116.Such excess air will be deflected horizontally toward wall 16 by theinclined electrode portion 120 and the top of ridge portion 122. Thecubic feet per minute of air and fibers entering applicator 18 and theeffective size of opening 102 will be adjusted such that an optimumquantity of fibers are delivered to electrode 28 while maintaining theamount of excess air passing through aperture 116 to an insignificantamount so as not to interfere with the action of the electrostatic fieldon the fibers.

It was found that without the converging side walls 96, the fibers wouldtend to flare laterally outwardly as they enter the field and fiberswould accumulate at the sides of the front section. However, with theconverging side walls 96 and the narrow width cutout 112 the tendency ofthe fibers to spread laterally is reduced. The slope of the side walls96 and the width of cutout 112 are chosen so that the fibers spreadsufficiently to optimize the effective width of electrode 28 withoutaccumulating fibers at the sides of the electrode. Other techniquescould be used either in connection with the converging side walls or inplace thereof. For example, the rear side of baflle 114 could be eitherscalloped or serrated to interfere with lateral motion of the fibers orthe baflle could be concave forwardly with either a smooth or a steppedhorizontal cross section. Various shapes are also contemplated forelectrode 28. For example, very satisfactory results were obtained withan electrode having a lower portion extending vertically downwardly fromthe front of the ridge portion 122 rather than being inclined slightlyrearwardly as described hereinabove.

It is to be understood that the dimensions of the applicator as shown inFIGS. 5-7 are not intended to be to scale. By way of example and notlimitation, in one particular applicator the width of the front section88 was 12", the width of the rear wall of the rear section 86 was 8",the height was approximately 11" and the depth of the applicator fromfront to back was 6 /2". Electrode 28 was 9 /2" high and slightly morethan 11'' wide. The opening 102 was 3" by 4", cutout 112 was IV! by 6"and the aperture 116 was 1" by 11". By way of further example, the innerdiameter of the inlet sleeve 90 and of hose 32 was 2" and blower 70 hada maximum capacity of c.f.m. Blowers having substantially highercapacities of say 240 c.f.m. may also be used to increase the quantityof fibers delivered to the applicator.

The method and the apparatus for electrostatic flocking have beendescribed hereinabove for purposes of illustration and are not intendedto define limits of the present invention the scope of which is definedby the following claims:

I claim:

1. The method of applying fibers to an object such as a wall or the likewherein an electrode is carried by a portable hand-held applicator andelectrical energy is operatively applied to said electrode to establishan electrostatic field in a first direction between said electrode andsaid object when said applicator is in proximity to said objectcomprising the steps of storing fibers in bulk at a location remote fromsaid applicator, establishing a confined current of air moving from saidremote location to said applicator, introducing loose fibers from saidbulk stored fibers into said moving air to thereby transport fibers fromsaid remote location to said applicator, separating fibers received atsaid applicator from said moving air, introducing the fibers soseparated into said electrostatic field in a direction generallyperpendicular to said first direction, causing said fibers to bepropelled to and deposited on said object under the influence of saidelectrostatic field, and directing said moving air after said fibershave been separated therefrom in a direction away from said firstdirection so that said moving air does not substantially interfere withthe propelling action of said electrostatic field on said fibers.

2. The method set forth in claim 1 wherein said fibers are separatedfrom said moving air at least in part at a location above said electrodewhile simultaneously minimizing motion components of said fibers alongsaid first direction and wherein said fibers are introduced into saidfield primarily due to gravity.

3. The method set forth in claim 1 further comprising introducingmoisture into said moving current of air at a location upstream of saidapplicator whereby said fibers are moistened prior to introduction intosaid field.

4. The method set forth in claim 3 wherein the introduction of moistureinto said moving air occurs at said remote location prior tointroduction of said loose fibers into said moving air.

5. An apparatus for depositing fibers as a coating on an object such ason a wall or the like comprising a portable hand-held applicator havingan electrode mounted thereon, an electrical power supply operativelycoupled to said electrode so as to establish an electrostatic fieldbetween said electrode and said object when said electrode is inproximity to said object and means for introducing fibers into saidfield comprising fiber storage means for storing fibers in bulk, saidstorage means being located remote from said applicator, conduit meansoperatively communicating with said storage means and with saidapplicator to form a passageway therebetween, fan means operativelycoupled with said conduit means to establish a current of air thereinmoving in a direction from said storage means to said applicator, andmeans for transferring fibers from said storage means into said movingair so that said fibers are transported by the moving air to saidapplicator to thereby provide a substantially continuous supply offibers at said applicator for introduction into said field during acoating operation, and wherein said applicator comprises a housinghaving an inlet therein communicating with said conduit means, deflectormeans mountedin said applicator housing and disposed between said inletand said electrode so as to direct fibers from said inlet in a directionalong a path in said applicator toward said electrode, said deflectormeans being perforated to allow moving air to pass therethrough and outof said housing while preventing the passage of fibers therethrough.

6. The apparatus set forth in claim 5 wherein said applicator furthercomprises bafile means mounted in said housing downstream of saiddeflector means to effect a final separation of fibers from moving airand introduce said finally separated fibers into said electrostaticfield.

7. The apparatus set forth in claim 6 wherein said inlet is arranged todirect fibers from said conduit means into said applicator in agenerally horizontal direction, said deflector means comprises apartition in said housing inclined upwardly and forwardly from belowsaid inlet and extending in front of said inlet toward the top of saidapplicator, said partition having an opening therethrough covered with afine mesh screen so that fibers striking said screen and said partitionare deflected upwardly and forwardly from said inlet while some of themoving air passes through said screen, said bafile means being mountedin said housing generally above and forwardly of said partition so thatat least some of the deflected fibers strike said baffle means, saidbaflle means being inclined downwardly and rearwardly so that airimpinging on said bafile means is deflected upwardly, the top of saidapplicator being open and covered with a fine mesh screen to allow airdeflected from said partition and said baffle means to pass out of saidapplicator housing while retaining fibers therein, the slope of saidbafile means being such that as the air deflected therefrom passes outof said housing the fibers striking said baflle means fall downwardlytherefrom due to gravity, and wherein said electrode is mounted belowsaid bafile means so that fibers falling from said bafiie means dropinto said field.

8. The apparatus set forth in claim 7 wherein said applicator hasvertical side walls converging laterally inwardly from said inlet towardsaid baffle means.

9. The apparatus set forth in claim 6 wherein said electrode is mountedon said applicator below said bafile means, said electrode has atransverse ridge thereon extending laterally of said applicator andprojecting forwardly thereof, said ridge having a generally flathorizontal top face, and means on said applicator to receive fibers fromsaid batfle means and direct the fibers downwardly toward said top face.

10. The apparatus set forth in claim 5 wherein said deflector meanscomprises a bafile portion and a perforated portion, said bafile portionbeing positioned so as to deflect said moving air through saidperforated portion, and wherein said perforated portion has perforationstherein dimensioned to prevent fibers from passing therethrough whilesaid fibers are directed in a direction along said path toward saidelectrode.

11. The apparatus set forth in claim 5 further comprising means forintroducing moisture into said current of air at a location remote fromsaid applicator so that said fibers are subjected to said moisture priorto introduction of said fibers into said applicator.

v References Cited WILLIAM D. MARTIN, Primary Examiner E. J. CABIC,Assistant Examiner US; Cl. X.R. 117-33; 118629, 640; 2393, 15

